Field of Invention
The present invention belongs to the wasted pressure recovery technology in fields of cryogenic liquefaction and cryogenic air separation, relates to a radial-axial type cryogenic liquid turbine, and more particularly to a cryogenic liquid turbine for throttling and decompressing low-temperature and high-pressure liquefied gases.
Description of Related Arts
Energy saving is the main part of and guarantee for the sustainable development strategy of global economy, and can effectively relieve the restriction of the energy bottleneck, so as to help to establish the energy-saving society. Recovering industrial wasted energy in large-scale energy consumption apparatuses is one of key measures of the energy saving, and has great social benefit and economic value. Cryogenic liquid turbine is a substitute product of liquid Joule-Thomson valve in the energy intensive low temperature cycle apparatuses of air separation, liquefied natural gas (LNG), etc. When satisfying a requirement that the pressure needs to be reduced in the technological process, the cryogenic liquid turbine can effectively suppress vaporization, avoid the destruction generated by cavitation and the irreversible loss of the energy of high-pressure liquefied gases, and use high-level pressure head recovered to generate electricity, which has considerable economic benefits.
In patent applications published in recent years, “rotor of expander for throttling high-pressure liquefied gases”, whose patent application number is CN200810150526.2; “liquid expander”, whose patent application number is CN200910023562.7; and “submerged liquid turbine for decreasing pressure of liquid natural gas” developed by Japanese Ebara company, whose patent application number is US2006/0186671A1 are related to the radial-axial type cryogenic liquid turbine. “Rotor of expander for throttling high-pressure liquefied gases” discloses a rotor of expander for throttling high-pressure liquefied gases, wherein, the rotor is in a horizontal structure with impeller cantilever for meeting the strict requirements of the media flow rate and the braking generators in the conventional liquid expander. The rotor is able to be braked by a conventional generator, pump, or air blower, and is appropriate for decreasing pressure of media with any flow rate. However, an oil slinger is used in the structure of the rotor, i.e., a rotating part is added in the structure so as to decrease the mechanical property of the rotor. “Liquid expander” discloses a single liquid phase expander for throttling liquid, which can solve problems of pressure-head loss and cavitation destruction that are caused by Joule-Thomson valve used in the conventional air separation process. However, “Liquid expander” has disadvantages as follows. 1) the cold loss of the liquid expander is relatively large, wherein one side of the nozzle chassis of the liquid expander is directly exposed in the air, and the other side thereof is the low temperature liquid refrigerant. Therefore, the cold loss through the nozzle chassis is very large, which decreases the efficiency of the liquid expander. In addition, the liquid expander uses the nozzle adjusting mechanism that gets through the nozzle chassis, which also increases the cold loss of the liquid expander and causes a result that the nozzle adjusting mechanism cannot be operated normally. 2) the nozzle cover plate is connected to the nozzle chassis only by the pin, and the compression margin of the compression spring of the nozzle cannot be adjusted, which increases the difficulty of orientation and installation in the axial direction while the precision is difficult to be guaranteed. 3) the diffuser tube of the impeller outlet and the nozzle assembly are manufactured as a whole, which increases the difficulty of axially orientating the complete machine. 4) the impeller outlet does not use any effective device for decelerating high-velocity media and subsequently raising its pressure, so at the impeller outlet, media velocity is high and the flow loss is large. The submerged liquid turbine developed by Japanese Ebara Company has disadvantages as follows. 1) the structure that turbine rotor and generator rotor are coaxial is used, so the impeller is of the same size as the generator and the volume of the complete machine is relatively large, which is only appropriate for applications of large flow rates; 2) the generator is completely immersed in low temperature media, so the requirement of cable materials of the generator, the requirement of the sealing performance of the generator, and the requirement of the insulating property of the generator are stringent; 3) the braking method is not flexible, wherein only electrical generator may be utilized for braking, and the submerged liquid turbine is not appropriate for using air blower and pump to brake.